The invention concerns a process for hydrophobization of microbacteria-proof air filter materials. Using this process such air filter materials are made hydrophobic for the purpose of retaining microparticles and microbial components of air and which are preferentially used in blood transfusion services, for infusion therapy, and in anaesthesia and surgery.
In almost all the fields of medicine, procedures are known during which liquids contained in a receptacle have to be conveyed to patients or to other containers. Often the transfer is possible only with simultaneous venting of the receptacles during use. In most cases, the moved volume is atmospheric air, which before reaching the respective receptacles has to be cleaned of microparticles. Cleaning of the air is effected by means of filter materials such as ceramics, papers, fleeces and membranes (compare Wirtschaftspatent WPB ol D/293 811.1, DD), which during this process or during interruptions for medical reasons may come into contact, with the liquids to be infused. This contact however, should always be avoided, since otherwise clogging of the filter pores may arise also a nutritive substrate for the conveyed microorganisms may originate. If this occurs, contamination of the transfer line may no longer be excluded, causing the transfer set as well as the preserved liquid to have to be discarded.
Therefore, the agents of hydrophobation used must meet special requirements. This means that they have to be physiologically unobjectionable, since they may come into contact both with air as well as with the liquids to be infused. Furthermore, the use of the hydrophobizing agent should not cause clogging of the filter pores and the hydrophobic effect must be maintained over a period of about 5 years.
The current level of technology is characterized by two procedures. In the first case, filter materials are used, which due to their chemical structure are already hydrophobic, e.g., membranes from polyethyleneterephthalate. In the second case, filter materials are used, which subsequently have to be treated with hydrophobizing agents.
The first-mentioned filter materials are suitable for use, with venting under a small differential pressure, but are relatively expensive to manufacture. The filters made of ceramics, paper, glass fleece, textiles, leather, or of other materials, which are hydrophobized subsequently, are considerably more simple to manufacture. Before put into use, however, they have to be treated unilaterally with a hydrophobizing agent which meets the respective requirements. The most well-known agents among them are paraffins, waxes, metallic soaps, with additives of aluminium- and zirconium salts, quarternary organic compounds, derivatives of urea, fatty acid modified melamine resins, complex chromium salts and silicone. During hydrophobization, the filter material maintain their porosity because of impregnation in the coating of individual fibres (see Rompps Chemie Lexikon, 8.sup.th Edition Frankh'sche Verlagshandlung, Stuttgart 1983). One hint given in the same source, stating that perfluoridized compounds also are suitable for hydrophobization, although they are predominantly used in oleophobation and soil resistance equipment, is of no importance for a process of hydrophobization of microbacteria-proof materials for air filters.